Electric variable tone percussion instrument

ABSTRACT

An electric variable tone percussion instrument comprises a source of periodic signals, storage means coupled to the source of periodic signals, output means coupled to the storage means and switching means coupled to the storage means, the switching means normally being in a non-conducting state, the storage means being charged to a maximum storage voltage and the output means producing an minimum output voltage while the switching means is in the non-conducting state, the storage means discharging and the output means producing a maximum output voltage when the switching means is in a conducting state, the switching means immediately returning to the non-conducting state causing the storage means to charge towards the maximum storage voltage while the output means produces an exponentially decaying output voltage signal.

United States Patent Cohen 1451 Apr. 11, 1972 [541 ELECTRIC VARIABLETONE 2,659,533 11/1953 Quinby et a1..., ..317/1)1o. 2 PERCUSSIONINSTRUMENT 3,112,476 11/1963 Cohler et a1. ..317/D1G. 2 3,493,791 2 1970Ad 10 et 1. ..317 DlG.2 [72] Inventor: Herbert Cohen, 180 West EndAvenue, es n 3 New York 10023 Primary Examiner-Laramie E. Askin 22Filed; [)m 14, 970 Assistant Examiner-U. Weldon Attorney-Peter L. Berger[21] App]. No.: 97,493

[57] ABSTRACT [52] U.S. Cl ..84/l.01, 84/].13, 84/].24, An electricvariable tone percussion instrument comprises 3 84/126 source ofperiodic signals, storage means coupled to the [51] IRLCI. ..G10h U00Source f periodic signals, output means Coupled to the [58] Field ofSearch ..84/D1G. 12, D10. 13,D1G. 8, storage means and Switching meanscoupled to the Storage 331/ means, the switching means normally being ina non-conducting state, the storage means being charged to a maximum[56] References cued storage voltage and the output means producing anminimum UNITED STATES PATENTS output voltage while the switchingmeans isin the non-conductmg state, the storage means d1scharg1ng and the output3,535,972 10/1970 Teran1sh1 ..84/1.26 means producing a maximum outputvoltage when the 3,571,482 1971 U h1y m switching means is in aconducting state, the switching means 5 1 971 immediately returning tothe non-conducting state causing the 3,141,919 7/1964 Mabuchlw. storagemeans to charge towards the maximum storage volt- 31283,057 1 H1966 page while the output means produces an exponentially decay- Prather t-33 X output voltage signal 3,427,562 2/1969 Lajoie et a1. ..331/l77 13,551,704 12/1970 Baum et a1 ..331/I11 X 11 Claims, 1 Drawing FigurePatented April 11, 1972 Inventor.

Herbert Cohen Airorney.

ELECTRIC VARIABLE TONE PERCUSSION INSTRUMENT BACKGROUND OF THE INVENTIONThis invention relates to a musical instrument, and more particularly,to an electric variable tone percussion instrument.

Interest in electric musical instruments has soared in recent years.There are electrical organs, guitars and other instruments which findwidespread and increasing usage and enjoy great popularity. In the fieldof percussion instruments, a wide variety of prior art devices exist.These devices have attendant disadvantages. They are relativelyexpensive and frequently are quite fragile. Additionally, the toneproduced can generally be varied only within a half or, at most, asingle octave range and the tone produced lacks the fullness andrichness desired for such an instrument. Such prior art devices haveincluded twin-T-RC networks used as oscillators producing sinusoidalsignals where the tone produced by the percussion instrument is tunablegenerally over one-half an octave. This limitation on the variation ofthe frequency of the signal or tone produced by the instrument hampersthe versatility of such instruments.

An object of my invention is to provide an improved electric variabletone percussion instrument.

Another object of this invention is to provide an electric variable tonepercussion instrument utilizing solid state devices.

Another object of this invention is to provide such a device which isrelatively reliable in operation and sturdy.

7 Still another object of my invention is to provide such a device whichis capable of producing a tone with a frequency variable over the entireaudible range.

Yet another object of this invention is to provide such a device whichproduces a rich, deep, full quality tone.

Another object of my invention is to produce such a device which isrelatively inexpensive to manufacture yet reliable, attractive andcompact.

Other objects, advantages and features of this invention will becomemore apparent from the following description.

SUMMARY OF THE INVENTION In accordance with the principles of myinvention, the above objects are accomplished by providing an electricvariable tone percussion instrument comprising means to produce aperiodic signal, storage means connected to the means to produce theperiodic signal, output means connected to the storage means andswitching means to discharge the storage means and provide anexponentially decaying signal across the output means.

In accordance with a feature of the invention, the periodic signal isproduced by a sawtooth wave generator being applied to the input of abistable multivibrator (flip-flop), the output of which is AC coupled tothe input of a bridge modulator having a capacitor connected across thebridge modulator. A resistor or load is connected across the output ofthe bridge modulator and the capacitor will charge to a predeterminedlevel, approximately the level of the supply voltage for the flipfiop,and remain in that state until discharged. A touch sensitive device isconnected to the gate of a thyristor which when switched ON causes thecapacitor to discharge, allowing a voltage to be present across theoutput load resistor. As the capacitor begins to charge again, theoutput across the resistor decays exponentially, thus providing anexponential decay signal which is amplified and supplied to a speaker.

The frequency of the sawtooth wave generator is variable and cantranscend the entire audible range thus providing an improvement overprior art devices where the frequency of the tone produced was variablegenerally within one-half an octave. Additionally, the touch sensitivedevice can be used to simulate a percussion instrument such as a drum sothat as the instrument is played, an electrical signal will be producedwhich is variable over the entire audible range.

As another feature of my invention, the sawtooth wave generator isprovided with transistor means for insuring the tum-off of aprogrammable unijunction transistor (PUT) utilized in the generator. Theuse of the transistor means insures the holding current through the PUTis not maintained after the PUT is switched ON. Further, the transistormeans permits a wide frequency adjustment to be achieved which isrelatively insensitive to current variations, even though the PUT isutil ized.

As another feature of my invention, the flip-flop is utilized to producesquare wave pulses adding a wide range of frequencies in the signalproduced thereby. Such a wide range of frequencies produces anextraordinary fullness and richness of tone which is not achievable withprior art devices where a sinusoidal signal is utilized.

IN THE DRAWING The accompanying FIG. is a schematic diagram of anembodiment of my invention.

DETAILED DESCRIPTION My invention is capable of being produced as asolid state device and is susceptible of being made on a printed circuitboard or as a hybrid circuit. This provides for maximum reliability andminimum size.

The variable tone percussion instrument is provided with a sawtooth wavegenerator 10 supplying an output to a flip-flop 12. The output of theflip-flop 12 is AC coupled to a diode modulator bridge 14 The output ofthe bridge 14 is connected across a load resistor 18 which provides anoutput signal carried through amplifier 20 and supplied to a speaker 22.The output produced by flipflop 12 is generally a periodic signal and,as a feature of the invention, is a square wave signal which, when ACcoupled to the modulator bridge 14, goes both positive and negative withrespect to ground.

The sawtooth wave oscillator 10 is a relaxation type and is providedwith a variable resistor or potentiometer 24 connected at one side to asource of positive potential and connected through a fixed resistor 26to a capacitor 28. Additionally, resistor 26 is connected to thecollector of an NPN- type transistor 30 connected in the groundedemitter mode, and to the anode 32 of a solid state switching device,such as a PUT 34, having its cathode 36 connected through a loadresistor 38 to ground. The gate 40 of PUT 34 is connected to a voltagedivider formed by resistors 42 and 44 connected between the source ofpositive potential 25 and ground, with the connection point betweenresistors 42 and 44 being connected to the gate 40 of the PUT.

The relaxation type sawtooth oscillator operates to produce periodicpulses in the following manner: the voltage divider formed by resistors42 and 44 maintains a fixed voltage at the gate electrode 40. Capacitor28, connected through resistor 26 and potentiometer 24 to the source ofpositive potential 25, charges with a time constant determined by thecapacitor 28 and the total resistance in the series path. This totalresistance is variable because of potentiometer 24. While the voltage atanode 32 is increasing and is less than the gate voltage, the PUT ismaintained in its normally OFF state. When the voltage at the anode 32of PUT 34 slightly exceeds the voltage at gate electrode 40, the PUT iscaused to conduct. To ensure that the PUT turns OFF after it isconducting, transistor 30 is switched ON when PUT 34 conducts since apositive voltage is developed across load resistor 38. The switching 0Nof transistor 30 pulls the collector voltage down to a value of severalmillivolts which ensures that the voltage across the PUT is maintainedlow and the current is drawn through transistor 30, thus bypassing PUT34. By utilizing the transistor as a current bypass or shunt, the valueat which potentiometer 24 can be set may be widely varied withoutaffecting the operation of the PUT. This follows because the holdingcurrent level required to hold the PUT conducting which includes astorage capacitor 16. a

after it is switched ON is not maintained once the transistor conducts.In this manner, a wide frequency variation can be produced which isrelatively insensitive to the change in current resulting from thevariation in the value of the potentiometer.

When PUT 34 conducts, a voltage spike is produced at the gate electrode40 and is coupled through a capacitor 50 to the cathodes of steeringdiodes 52 of flip-flop 12. A resistor 54 is connected from the cathodesof the steering diodes 52 to a point of reference potential or ground56. The flip-flop 12 is conventional and is provided with NPN-typetransistors 58 having their collectors connected through load resistors60 to a source of positive potential. A parallel combination of resistor62 and capacitor 64 connects the collector of one of the transistors 58to the base of the other transistor coupling the collector voltage tothe base of the other transistor and changing the state of the flip-flop12 with the occurrence of each spike at gate 40. The flip-flop 12 servesas a frequency divider, and more importantly as a means coupled withsawtooth oscillator to produce a periodic signal, which is a square wavesymmetrical with respect to time. The frequency at which such squarewaves are produced at the collector of transistor 58 is dependent uponthe time constant of the sawtooth relaxation type oscillator 10.

The output of flip-flop 12 is connected through an AC coupler comprisinga resistor 66, having one end connected to the collector of one of thetransistors 58 while the other end is connected through a capacitor 68to one end of a diode bridge modulator 14. The diode bridge modulator isprovided with diodes 70, 72, 74 and 76. The anode of diode 70 isconnected to the cathode of diode 72 and to capacitor 68. The cathode ofdiode 70 is connected to the cathode of diode 74 while the anode ofdiode 72 is connected to the anode of diode 76. The cathode of diode 76is connected to the anode of diode 74 and through load resistor 18 tothe source of reference potential or ground 56. A storage means ordevice, such as capacitor 16, is connected across the diode bridge andis connected between the cathode of diode 70 and the anode of diode 72.The diodes are connected in the conventional manner so that current canflow through capacitor 16 in only one direction, and since the ACcoupling, including resistor 66 and capacitor 68, couples the output offlip-flop 12 to the input of bridge modulator 14, the capacitor 16 willcharge to a predetermined value with a time constant determined by thevalue of capacitors 16 and 68, resistors 66, 60 and 18, and the nominalresistance values of the diodes when conducting. Resistor 66 also servesas a 'decoupler to minimize the loading down of the output of flipflop12. The capacitor 16 will charge to the predetermined value and maintainthat charge, and therefore, zero current flows through the bridge andacross output resistor 18 providing a zero voltage level across theresistor.

In accordance with a feature of my invention, a switch means, such as agated silicon control rectifier (SCR) 78 is utilized to dischargecapacitor 16. The gated SCR serves as a conventional switching deviceand its anode and cathode are connected across capacitor 16. The SCRoperates in the following manner: it is in a non-conducting state untila triggering pulse is applied to the gate 80 of the SCR 78 which causesthe SCR to conduct. It will conduct as long as the current flowingtherethrough is greater than a holding current level. When a personsfinger or hand touches a touch sensitive contact 82, the capacity of thecontact changes slightly and stray RF or AC signals which are induced inthe body become amplified by an NPN-transistor 84. The collector oftransistor 84 is connected to the anode of SCR 78 while the emitter oftransistor 74 is connected to the gate electrode 80 and through a gateload resistor 86 to the anode of diode 72.

The bridge modulator operates in the following manner: the capacitor 16charges to the predetermined level and will maintain that charge as longas SCR 78 is non-conducting. When the finger or hand touches touchsensitive contact 82, SCR 78 is triggered, capacitor 16 dischargescompletely through the SC R thus causing a DC current to flow throughthe bridge and load resistor 18, thereby providing a maximum voltagesignal across the resistor. The holding current level required to keepthe SCR 78 in its conducting state is not maintained and thus SCR 78immediately turns OFF, thereby allowing capacitor 16 to recharge. Therecharging of capacitor 16 causes an exponentially decaying signal toappear at the output of the device, that is across resistor 18. It mustbe remembered that the signal supplied to the input of the bridgemodulator 14 is a square wave produced by the flip-flop 12 having afrequency determined by the value of potentiometer 24. Therefore, theexponentially decaying signal appearing across resistor 18 is a squarewave signal which is exponentially decaying in amplitude. lt is wellknown that square wave signals contain a multitude of harmonics, and thesignal provided across resistor 18 which is carried through amplifier 20and supplied to speaker 22 is a rich, deep, full tone which is capableof being varied over the entire audible range. The exponential decayacross resistor 18 is responsible for the percussive sound, and it hasbeen found that the sound produced is extremely attractive andinteresting and not available with prior art devices.

In accordance with a feature of my invention, the gate load resistor 86ensures that SCR 78 will not conduct inadvertently. The gate loadresistor also increases the holding current level of the SCR whichprevents the conducting state being maintained after it initially isswitched ON.

It may be understood that my invention provides a signal which is richin harmonic content and when amplified by amplifier 20 and supplied tospeaker 22, will produce an unusual, interesting and attractive sound ortone.

It can be appreciated that any signal source providing a specific orfinite number of periodic signal may be applied to the input ofmodulator l4, and the flip-flop utilized in my invention provides theadditional advantage of producing a signal rich in harmonic content atthe output. The exponential decay rate may also be varied by changingthe RC time constant in the path including capacitors l6 and 68 andresistors 66, 60 and 18. This variation may be conveniently achieved bymaking resistor 66 a potentiometer.

Touch sensitive contact 82 is also illustrative of a device which issensitive to the signals carried in a persons body, but any devicesensitive to the movement of hands could be utilized to trigger the SCRto produce the exponentially decaying output signal produced by myinvention. For instance, a photocell could be used and the degree ofshading obtained in a light field as sensed by the photocell woulddetermine whether or not the SCR were to be switched ON and couldsimultaneously be used to adjust or vary the frequency of the relaxationtype oscillator. As an alternative, the photocell arrangement could beused solely for determining the frequency output of the variable tonedevice with the frequency continuously variable as the amount of lightwithin the field of the photocell is varied.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above apparatus withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description and shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

lclaim:

1. An electric variable tone percussion instrument comprising a sourceof a finite number of periodic signals, means connected to said sourcefor continuously varying the frequency of said periodic signals, bridgemodulator means coupled to said source, said bridge modulator meanscontains a storage means output means coupled to said bridge modulatormeans, and switch means coupled to said storage means, said switch meansnormally being in a non-conducting state, said storage means beingcharged to a maximum voltage and said output means producing a minimumoutput voltage while said switch means is in said non-conducting state,said storage means discharging and said output means producing a maximumoutput voltage when said switch means is in a conducting state,

said switch means immediately returning to said non-conducting statecausing said storage means to charge towards said maximum storagevoltage while said output means produces an exponentially decayingoutput voltage signal.

2. An electric variable tone percussion instrument as set forth in claim1, wherein said periodic signals are square waves. t

3. An electric variable tone percussion instrument as set forth in claim2, wherein said storage means is a capacitor.

4. An electric variable tone percussion instrument as set forth in claim1, wherein said means for varying the frequency of said periodic signalscomprises means for varying said frequency continuously through theaudio range,

5. An electric variable tone percussion instrument as set forth in claim4, wherein said means for adjusting the frequency is a potentiometer,and said source of periodic signals includes a solid state switchingdevice, said potentiometer being coupled to said switching device, andmeans for returning said switching device to a non-conducting stateafter said switching device conducts by maintaining the amount ofcurrent flowing through said switching device at less than a holdingcurrent level independently of the setting of said potentiometer.

6. An electric variable tone percussion instrument as set forth in claim5, wherein said means for returning includes a transistor being causedto conduct when said switching device conducts.

7. An electric variable tone percussion instrument as set forth in claim4, wherein said source comprises a relaxation type oscillator coupled toa bistable multivibrator, said oscillator including a programmableunijunction transistor having an anode, cathode and gate electrodes,said programmable unijunction transistor being non-conducting when thevoltage at said anode is less than the voltage at said gate electrode, a

capacitor and a potentiometer connected between a source of positivepotential and ground, said capacitor being coupled to said anode andcharging in accordance with a time constant determined by said capacitorand said potentiometer, said programmable unijunction transistorconducting when said capacitor charges to a voltage greater than thevoltage at said gate electrode, a transistor having base, emitter andcollector electrodes, said base electrode being connected to saidcathode electrode, said collector electrode being connected to saidanode electrode and said emitter electrode being connected to ground,said transistor conducting when said programmable unijunction transistorconducts ensuring that said programmable unijunction transistor becomesnon-conducting after becoming conducting.

8. An electric variable tone percussion instrument as set forth in claim1, including a touch sensitive contact, said switch means beingtriggered into said conducting state when said touch sensitive contactis manually touched.

9. An electric variable tone percussion instrument as set forth in claim3, said bridge modulator means including diode means connected to saidcapacitor for allowing current to flow through said capacitor in onlyone direction enabling said capacitor to charge to said maximum storagevoltage.

10. An electric variable tone percussion instrument as set forth inclaim 9, wherein said bridge modulator means having an output, saidoutput means being connected across said output of-said bridgemodulator.

11. An electric variable tone percussion instrument as set forth inclaim 10, wherein said switch means is connected across said capacitor,said switch means being provided with a gate electrode connected to atouch sensitive contact, said touch sensitive contact producing atriggering signal when manually touched causing said switch means to bein a conducting state discharging said capacitor.

1. An electric variable tone percussion instrument comprising a sourceof a finite number of periodic signals, means connected to said sourcefor continuously varying the frequency of said periodic signals, bridgemodulator means coupled to said source, said bridge modulator meanscontains a storage means output means coupled to said bridge modulatormeans, and switch means coupled to said storage means, said switch meansnormally being in a nonconducting state, said storage means beingcharged to a maximum voltage and said output means producing a minimumoutput voltage while said switch means is in said non-conducting state,said storage means discharging and said output means producing a maximumoutput voltage when said switch means is in a conducting state, saidswitch means immediately returning to said nonconducting state causingsaid storage means to charge towards said maximum storage voltage whilesaid output means produces an exponentially decaying output voltagesignal.
 2. An electric variable tone percussion instrument as set forthin claim 1, wherein said periodic signals are square waves.
 3. Anelectric variable tone percussion instrument as set forth in claim 2,wherein said storage means is a capacitor.
 4. An electric variable tonepercussion instrument as set forth in claim 1, wherein said means forvarying the frequency of said periodic signals comprises means forvarying said frequency continuously through the audio range.
 5. Anelectric variable tone percussion instrument as set forth in claim 4,wherein said means for adjusting the frequency is a potentiometer, andsaid source of periodic signals includes a solid state switching device,said potentiometer being coupled to said switching device, and means forreturning said switching device to a non-conducting state after saidswitching device conducts by maintaining the amount of current flowingthrough said switching device at less than a holding current levelindependently of the setting of said potentiometer.
 6. An electricvariable tone percussion instrument as set forth in claim 5, whereinsaid means for returning includes a transistor being caused to conductwhen said switching device conducts.
 7. An electric variable tonepercussion instrument as set forth in claim 4, wherein said sourcecomprises a relaxation type oscillator coupled to a bistablemultivibrator, said oscillator including a programmable unijunctiontransistor having an anode, cathode and gate electrodes, saidprogrammable unijunction transistor being non-conducting when thevOltage at said anode is less than the voltage at said gate electrode, acapacitor and a potentiometer connected between a source of positivepotential and ground, said capacitor being coupled to said anode andcharging in accordance with a time constant determined by said capacitorand said potentiometer, said programmable unijunction transistorconducting when said capacitor charges to a voltage greater than thevoltage at said gate electrode, a transistor having base, emitter andcollector electrodes, said base electrode being connected to saidcathode electrode, said collector electrode being connected to saidanode electrode and said emitter electrode being connected to ground,said transistor conducting when said programmable unijunction transistorconducts ensuring that said programmable unijunction transistor becomesnon-conducting after becoming conducting.
 8. An electric variable tonepercussion instrument as set forth in claim 1, including a touchsensitive contact, said switch means being triggered into saidconducting state when said touch sensitive contact is manually touched.9. An electric variable tone percussion instrument as set forth in claim3, said bridge modulator means including diode means connected to saidcapacitor for allowing current to flow through said capacitor in onlyone direction enabling said capacitor to charge to said maximum storagevoltage.
 10. An electric variable tone percussion instrument as setforth in claim 9, wherein said bridge modulator means having an output,said output means being connected across said output of said bridgemodulator.
 11. An electric variable tone percussion instrument as setforth in claim 10, wherein said switch means is connected across saidcapacitor, said switch means being provided with a gate electrodeconnected to a touch sensitive contact, said touch sensitive contactproducing a triggering signal when manually touched causing said switchmeans to be in a conducting state discharging said capacitor.